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%I #10 Aug 17 2018 10:49:35
%S 1,3,6,10,21,36,45,78,105,210,276,325,496,561,630,703,741,903,1830,
%T 2145,2701,5050,6105,6903,8385,9870,10585,12561,14365,18145,18721,
%U 23436,25878,29890,30381,32385,36585,38503,38781,41616,47278,50721
%N Triangular numbers with property that digits alternate in parity.
%H Giovanni Resta, <a href="/A068882/b068882.txt">Table of n, a(n) for n = 1..10000</a>
%e 1830 is a term as 1, 8, 3 and 0 have odd and even parity alternately.
%t altQ[n_] := n < 10 || Union[ Total /@ Partition[ Mod[ IntegerDigits@n, 2], 2, 1]] == {1}; t[n_] := n (n + 1)/2; Select[ t@ Range@ 400, altQ] (* _Giovanni Resta_, Aug 17 2018 *)
%Y Cf. A068876, A030152.
%K nonn,base
%O 1,2
%A _Amarnath Murthy_, Mar 19 2002
%E More terms from _Sascha Kurz_, Mar 23 2002
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